Age at Onset, Survival Duration, and Cognitive Performance in Probable Alzheimer's Disease.

The relative importance of age at onset, survival duration past testing, symptom duration, and education as predictors of cognitive performance was assessed in 50 patients with moderately severe dementia of the Alzheimer type. Survival past testing and duration of symptoms prior to assessment emerged as the strongest predictors of cognitive performance, and education effects were noted for several verbal tests. A robust association emerged between cognitive impairment and nearness to death. This association, first noted in studies of "normal" aging, requires further exploration. Age-at-onset effects, with poorer performance in early-onset disease, were observed only for a few measures.